1. Field Of The Invention
The present invention relates to medical instruments and a method for their use and pertains particularly to an improved instrument system for accurately preparing and shaping distal femur and proximal tibia end surfaces to receive a knee prosthesis secured thereto.
2. Prior Art
In recent times knee surgery for the repair and/or replacement of knee joints has become increasingly common. Such total knee implant, when properly installed, will closely approximate or mimic natural knee movement. Even with such improvement in total knee structures, however, there still exists the problem of properly fitting and installing such prosthesis. Heretofore, with the surgical instruments available, a surgeon installing such implant must have had a high degree of skill in order to achieve optimum fit and alignment. It has therefore been recognized that it is desirable to provide an effective system of instruments and method for their use to insure a high degree of success in the preparation of the distal femur and proximal tibial ends to receive a prosthesis secured thereto.
Even prior to the present invention the need to provide such a system suitable for use by even a less skilled surgeon to reliably and efficiently prepare distal femur and proximal tibia ends for receiving a knee prosthesis has resulted in the development of several systems. One such system is shown in a patent by Petersen, U.S. Pat. No. 4,524,766 that involves a surgical knee alignment and cutting guide system and method. This system references a patient's mechanical axis and from that determination provides cutting guides for selective attachment for shaping the patient's proximal tibia to receive the tibia portion of the knee prosthesis and mounts cutting guides from the tibia components for appropriately shaping the distal femoral end to receive the femur portion of that knee prosthesis. Where the present invention is intended to accomplish the same result, the structure thereof and its use are decidedly distinct from this device. Particularly, for shaping the tibia proximal end, the present invention involves an elongate extensible support frame that, unlike the Petersen system, provides for a close calibration of length adjustment capability. Additionally, unlike this earlier Petersen patent that references from the tibia, the present invention references from the patient's distal femur and provides for locating the patient's mechanical axis from their anatomical axis, and after referencing that mechanical axis, employs an alignment guide and cutting guides that are distinct from those of the Petersen patent.
Another system for shaping the distal femur is shown in a patent by Lacey, U.S. Pat. No. 4,502,483. This patent, like the present invention, provides for locating a patient's mechanical axis relative to their anatomical axis and accordingly then locates and secures a femoral distal cutting guide to that bone end to form a first cut across the femoral condyle. From this first cut, the distal femur end is cut at a right angle to the patient's mechanical axis. Like the Lacey patent, the present invention references the patient's mechanical axis and provides for establishing a desired angle to their femur anatomical axis to calculate that mechanical axis. The cutting guides of Lacey, however, are structurally different from those taught by the present invention, and, of course, the Lacey patent does not involve a length adjustable tibial cutting guide as does the present invention.
The present invention provides a set of alignment and cutting guides and method for their use that is easier and more reliable for a surgeon to operate with as compared with earlier arrangements and provides a system that even a surgeon who has limited experience in total knee reconstruction surgery can use. The present invention provides a surgeon with the capability to simply and accurately prepare distal femur and proximal tibial bone ends to receive a preferred knee prosthesis fixed thereto within a time frame that is reasonable for the performance of the surgical procedure.